Offshore structure support and foundation for use with a wind turbine and an associated method of assembly

ABSTRACT

A pile based braced caisson structural support device includes a number of legs in is used to support a wind turbine. The wind turbine includes a base, a turbine generator and a blade mechanism. The legs are configured in a teepee type configuration such that the footprint of the base is larger than the footprint of the opposing end. This structural support can be used as a base for an offshore platform in that the support reduces the lateral forces on the support caused by wave action.

This application claims priority to U.S. Provisional Application No.60/626,912, filed on Nov. 12, 2004, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

This invention generally relates to structural supports. In particular,this invention relates to structural supports for, for example, windturbines, or the like.

2. Description Of Related Art

Conventional offshore platforms have deck legs that are vertical or arebattered outward as they extend downwards. The conventional arrangementprovides structurally efficient support for the deck but the associateddimensions of the platform at the water surface result in increasedexpense for the platform.

Wind turbines have traditionally been supported on mono-piles whenplaced offshore. However, recently, efforts have taken place to positionwind turbines in deeper water (approximately six to seven or more milesoffshore) in part to increase the aesthetics of the view from theshoreline. However, with the movement of wind turbines further offshore,the employment of mono-piles as the base on which wind turbines areplaced has become less cost effective.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a wind turbine incombination with a structure support that provides a sturdy and costeffective support even in deep waters. This combination includes a windturbine comprising a base and a blade mechanism. The structure supportfurther includes at least three elements configured in a substantiallyteepee shaped configuration, where the at least three elementsencompassing a substantially vertical member. A first end of the atleast three elements is capable of being affixed to a structure and asecond end of the at least three elements adapted to be in contact witha surface. The at least three elements intersect between the first endand the second end. The combination also includes a mounting flangeconnecting the structure support to the wind turbine.

In accordance with a further embodiment of the present invention the atleast three elements intersect above a waterline or at a waterline.

In accordance with another exemplary aspect of the present invention, amethod of constructing a wind turbine on a structure support isdisclosed. At least three legs are provided in a teepee configuration. Afirst end of the first three legs are placed on a mounting surface and adeck is affixed to a second end of the at least three legs. A windturbine mounting flange is affixed to the structure and a base isaffixed to the mounting frame and turbine element is affixed to thebase. A blade mechanism affixed to the turbine element.

These and other features and advantages of this invention are describedin or are apparent from the following detailed description of theembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention will be described in detail, withreference to the following figures, wherein:

FIG. 1 is a view in side elevation of an offshore platform according tothe present invention;

FIG. 2 is a view in front elevation of the offshore platform accordingto the present invention;

FIG. 3 is a perspective view of the offshore platform with a windturbine placed on a deck of the platform according to the presentinvention;

FIG. 4 is a side perspective view of the offshore platform with a windturbine placed on the deck of the platform according to the presentinvention;

FIGS. 5-18 illustrate an exemplary method of assembling the offshorestructure and wind turbine according to this invention;

FIGS. 19-21 illustrate nnother exemplary method of assembling theoffshore structure and wind turbine according to this invention;

FIGS. 22 and 23 illustrate another exemplary offshore structure supportfoundation according to this invention.

DETAILED DESCRIPTION OF THE INVENTION

The exemplary embodiments of this invention will be described inrelation to a support structure, such as an oil and gas platform or aplatform for the placement of additional structures, supported by threepiles and a central vertical member, such as drill pipe. However, toavoid unnecessarily obscuring the present invention, the followingdescription omits well-known structures and devices that may be shown inblock diagram form or otherwise summarized. For the purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the present invention. It should beappreciated that the present invention may be practiced in a variety ofways beyond these specific details. For example, the systems and methodsof this invention can be generally expanded and applied to support anytype of structure. Furthermore, while exemplary distances and scales areshown in the figures, it is to be appreciated the systems and methods ofthis invention can be varied to fit any particular implementation.

FIGS. 1 and 2 show an inward battered guide offshore platform indicatedgenerally at 10 in which battered bracing piles 12 a, 12 c and 12 e arearranged so as to minimize platform dimensions at the water surface 14while maximizing the spacing of the piles as they extend upward from thewater surface so that loads from a deck 16 at the top of the piles aretransferred directly to the piling. For example, if three or more pilesare employed to create the structure, they could be spaced apart 120degrees. Piles 12 b and 12 d are conductor piles used in oil and gasplatforms.

The platform includes a pile guide structure 18 which fits over and isconnected to a central vertical member 20 to receive the piles 12 a, 12c and 12 e at the water surface. The piles extend angularly throughguides 22 of the pile guide structure in such a manner that the distancebetween piles is minimized at the water surface, but the distancesbetween angled piles is maximized both at the ends supporting the deck16 as well as at the opposed end buried below the mudline 24. The pileguide connects the piles to act in unison to restrain lateral movementof the entire offshore platform 10 including the central vertical member20.

The pile guide 18 also supports appurtenances such as ladders, boatlandings, stairs, or the like, so that they can be installed in thefield as a unit, thereby, for example, reducing installation expense forthe platform. The legs 26 of the deck structure are connected to thetops of the piles. The increased pile spacing at the pile tops provides,for example, more structurally efficient support for the deck, reducedstructural vibration periods for the platform and increased resistanceto the rotation that results if the deck mass is eccentric to thecentral vertical member 20 than if the deck is supported by the centralmember. All field connections can be made above the water surface wherestructural integrity of the connections can be more easily verified thanif the connections were made below the water surface.

Once the piles 12 a, 12 c and 12 e are in place, and the legs 26 anddeck 16 are placed on the piles then, as shown in FIGS. 3 and 4, a windturbine 100 can be installed. FIGS. 3 and 4 show two differentperspective views of the wind turbine 100 when installed on the deck 16of platform 10. The wind turbine 100 comprises: a base 125 including alower section 110 and an upper section 120; a turbine element 130; and ablade mechanism 150 that comprises a rotor star 152 and individualblades 154. While the wind turbine described herein comprises a base 125and three individual blades 154, other types of wind turbines can alsobe employed with the structure of FIG. 1, for example, in the mannerdescribed above. For example, a wind turbine with a single base part orhaving a multitude of parts that make up the base can be employed.Moreover, the wind turbine can also include more or a lesser number ofblades as well as different types of blade mechanisms.

FIGS. 5-19 illustrate an exemplary method for assembling a the platform10 and wind turbine 100 in accordance with an exemplary embodiment ofthis invention with, for example, a barge boat, around a substantiallyvertical member 20 such as SSC 50 (Self Sustaining Caisson). In thisexemplary embodiment, the SSC 50 has been installed by an oil and gasdrilling rig, such as a rig drilling an exploration well. The verticalmember 20 (SSC 50) can either be installed when the platform isassembled or alternately, the remaining parts of the platform can beassembled around a previously erected vertical member. This enables theplatform to be advantageously built on existing already used oil drillcaissons or mono-piles to support oil and gas wells.

In FIG. 5, the position and orientation of the legs are determined and alift boat 55 anchored and jacked-up relative to the installation pointof the SSC 50. Next, as illustrated in FIG. 6, the guide structure 18 isunloaded from the barge 60. Then, as illustrated in FIG. 7, the piles 12a, 12 c and 12 e, are unloaded, placed in the guide structure, and inFIG. 8, installed via the guide structure into, for example, the oceanfloor with the aid of a pile driving hammer (e.g., a hydraulic hammer).As can be seen from this illustration, the piles 12 a, 12 c and 12 eintersect at a point just above the water line. This allows, forexample, the piles and all associated connections to be made abovewater. However, one would also understand that the intersection pointcould also reside at or below the waterline.

In FIG. 9, the barge 60 is relocated and the deck 16 is unloaded. InFIG. 10 the deck 16 including legs 26 are installed on the piles. Inaccordance with an exemplary embodiment of the invention, the deck canbe modified to employ and support a wind turbine 100. Specifically tosupport the turbine a mounted flange can be built on the deck 16. Theflange can be attached to the deck via bolting, grouting or welding.Although as illustrated in FIG. 10, the mounting flange 200 is shownbeing attached to the deck prior to placement on the legs 26, themounting flange 200 could be installed after the deck has beeninstalled. FIGS. 11 and 12 provide a side view and top view of the deck16 and mounting flange 200 when installed.

As illustrated in FIG. 13, once the mounting flange 200 is placed andset onto the deck 16, the tower lower section 110 is unloaded from thelift boat 55 and installed onto the mounting frame 200. Next, asillustrated in FIG. 14, the upper section 120 of the tower is unloadedand installed onto the tower lower section 110. Once the upper section120 of the base has been installed, as illustrated in FIGS. 15 and 16,the turbine 130 is removed from the lift boat and attached to the uppersection 120 of the tower.

As the tower lower section 110, tower upper section 120 and turbine 130are installed, the blade mechanism 150 is readied for installation. Theinstallation of this part of the wind turbine 100 can be performed in aplurality of different ways, in accordance with the present invention,as discussed below.

In accordance with one exemplary embodiment of the present invention, asillustrated in FIGS. 17 and 18, the complete, blade mechanism alreadyfully assembled is unloaded from the lift boat 55 and attached to theturbine 130.

Alternatively, as illustrated in FIGS. 19-21, the blade mechanism doesnot need to be fully assembled prior to attachment to the turbine 130.This is advantageous for several different reasons. The blade mechanism,if fully assembled would require extra stowage area for transport to theassembly area. If, for example, only two of the blades were assembled,then to the rotor star, then the required space needed to transport theblade mechanism is reduced. Furthermore, if the remaining blade is notattached to the rotor star until it is already attached to the turbine,additional monetary savings can be achieved since the crane employed toattach the blade can be smaller. In FIG. 19, the blade mechanism havingthe two blades attached to the rotor star is raised (via a crane) andattached to the turbine (as illustrated in FIG. 20). Finally, in FIG.21, the remaining blade 158 is attached to the rotor star. Again, FIGS.3 and 4 provide a side views of the assembled wind turbine on theoffshore structure support 10.

In accordance with another exemplary aspect of the present invention, adeck and associated mounting flange 300 is provided to receive a windturbine, as illustrated in FIGS. 22 and 23. Specifically, the mountingflange 300 includes a body 310 and an elliptical (or spherical) head 320extending below deck 16. The body 310 is circular and includes a deckend 312 and a head end 314 portion. A wind turbine 100 is able to beattached to the foundation body 310 at the deck end 312 of thefoundation body, via bolting, for example. The foundation body 310 isalso able to receive legs 26 that are connected to the batter bracingpiles 12a, 12c and 12e. Note that four piles are illustrated in FIG. 22.

The elliptical (or spherical) head 320 is attached to the foundationbody 310 at its deck leg connection end and enables the turbinefoundation 300 a more fatigue resistant connection at the deck leg. Forthis same reason, as illustrated in FIG. 22, the ends of the legs 26also employ a curved surface. By making the intersection between thefoundation body 310 and the elliptical (or spherical) head 320 as wellas foundation body 310 and the elliptical shape of the legs 26, acontinuously curved intersection is provide and a sharp corner isavoided. As a result, hot spot stresses are reduced on the joints.

Additionally in accordance with the present embodiment discussed withregard to FIGS. 22 and 23, the deck 16 includes structural supportelements extending from the deck end of the turbine foundation to theedge of the deck 16. While the deck 16 in the embodiment shown in FIG.23 is illustrated as octagonal, one could understand that the deck couldbe made to be other shapes also, (e.g., hexagonal, rectangular,circular, or the like).

In accordance with another aspect of the present invention, the naturalperiod of the offshore support structure can be adjusted to avoid theexcessive vibration of the wind turbine while operating that wouldresult if the natural period of the support structure was too close tomatching the rotational period of the turbine. This tuning of thenatural period can be accomplished by changing the size of thecomponents of the support structure, by increasing or decreasing thebatter of the piles, adjusting the spacing of the piles and/or byraising or lowering the elevations where the piles are laterallysupported. The extent and combination of tuning measures required varydepending on the design and operational characteristics of the windturbine and the water depth, meteorological and oceanographic conditionsand soil characteristics at the location.

For example, a typical three blade wind turbine is controlled byadjusting blade pitch to make one rotation about every 4.5 seconds inmost wind conditions. Therefore, for a typical wind turbine one of thethree blades would than pass the wind turbine support tower every 1.5seconds. To avoid the wind turbine rotational periods and limitpotential for destructive resonance, frequency forbidden zones areestablished for the natural frequency of the entire support structure.For a typical wind turbine the forbidden natural frequency zones couldbe 0.18 Hz to 0.28 Hz and 0.50 Hz to 0.80 Hz. Likewise, the targetnatural frequency would be 0.30 Hz to 0.33 Hz and higher order naturalfrequencies should be above 0.80 Hz. If computed eignfrequencies are ina forbidden zone tuning will be necessary. Tuning can then beaccomplished in the manner discussed above.

It is, therefore, apparent that there has been provided, in accordancewith the present invention, a support and method for assembling a windturbine for placement on an offshore support structure. While thisinvention has been described in conjunction with a number ofillustrative embodiments, it is evident that many alternatives,modifications, and variations would be or are apparent to those ofordinary skill in the applicable arts. Accordingly, the disclosure isintended to embrace all such alternatives, modifications, equivalentsand variations that are within in the spirit and scope of thisinvention.

1. A wind turbine in combination with a structure support comprising: awind turbine comprising a base; a structure support, said structuresupport further comprising at least three elements configured in asubstantially teepee shaped configuration, wherein the at least threeelements encompassing a vertical member; a first end of the at leastthree elements capable of being affixed to a structure; and a second endof the at least three elements adapted to be in contact with a surface,wherein the at least three elements intersect between the first end andthe second end; and a mounting flange connecting the structure supportto the wind turbine.
 2. The structure of claim 1, wherein the surface isa sea floor and the second end extends below a mudline.
 3. The supportof claim 1, where the at least three elements intersect above awaterline or at a waterline.
 4. The support of claim 1, wherein anangular guide maintains an orientation at least between the at leastthree elements.
 5. The support of claim 1, wherein the at least threeelements are offset from each other by 120°.
 6. The support of claim 1,wherein the wind turbine further comprises a blade mechanism.
 7. Thesupport of claim 1, wherein the structure support further comprises adeck on which the mounting frame is fastened.
 8. The support of claim 7,wherein the mounting frame includes a foundation body and an ellipticalhead extending below the deck.
 9. The support of claim 1, wherein thewind turbine further comprises a turbine element placed on the base andconnecting to the blade mechanism.
 10. A method of constructing a windturbine on a structure support comprising: providing at least three legsin a teepee configuration; placing an first end of the first three legson a surface; affixing a deck to a second end of the at least threelegs; affixing a wind turbine mounting flange to the structure; affixinga base to the mounting frame; affixing a turbine element to the mountingframe; and affixing a blade mechanism to the turbine.
 11. The method ofclaim 10, wherein the structure is located at a position above anintersecting point of the at least three legs.
 12. The method of claim10, wherein a guide structure is used to orient the at least three legs.13. The method of claim 10, further comprising: tuning the naturalperiod of the wind turbine so that the wind turbine and structureoperate at a predetermined frequency.
 14. The method of claim 13,wherein the natural period is tuned by adjusting the spacing between thethree legs.
 15. The method of claim 10, wherein the three legs areattached to the mounting frame.
 16. The method of claim 15, wherein themounting frame includes a foundation body and an elliptical head, andwherein the three legs are attached to the foundation body of theelliptical head.